Conventionally, there have been known a thermistor element which performs temperature measurement through use of a thermistor main body formed of an electrically conductive sintered oxide which has electrical conductivity and whose resistance changes with temperature, and a temperature sensor using such a thermistor element. For example, Japanese Patent No. 4990256 discloses a temperature sensing device (thermistor element) in which a temperature sensing element (thermistor main body) having a rectangular parallelepiped shape is covered and sealed with an inner protection layer (first covering layer). In Japanese Patent No. 4990256, a temperature sensing element having electrode wires (leads) joined thereto in advance is dipped into a glass paste prepared by mixing powder of crystallized glass and solvent such that the glass paste adheres to the temperature sensing element, followed by heat treatment, whereby an inner protection layer is formed.